Polyvinyl alcohol fibers and films with mineral fillers and small cellulose particles

ABSTRACT

The present invention is directed to an article of manufacture, which can be a fiber and or a film. In one aspect, the fiber or the film comprises a polyvinyl alcohol (PVOH) and an inorganic filler comprising particles having an average diameter of less than about 20 micrometers. The PVOH has a degree of hydrolysis of greater than about 95% and is present in a range between about 20 wt. % and about 99 wt. % based on the total fiber weight. Methods of making the fibers and films are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on U.S. Provisional Patent Application No.61/978,336, filed Apr. 11, 2014, which is incorporated herein in itsentirety.

TECHNICAL FIELD

The present invention is directed generally to polyvinyl alcohol (PVOH)fibers and films. More specifically, the invention is related PVOHfibers and films comprising fillers.

BACKGROUND OF THE INVENTION

Polyvinyl alcohol (PVOH) binder fibers are useful for increasing thestrength of paper products, although fiber cost can be prohibitive formany applications. Fiber cost can be mitigated by introducing fillersthat are cheaper than PVOH. However, alternative fibers that incorporaterecycled materials as fillers may not be suitable for white paperproducts because fibers produced are dark in color.

Bright fillers, such as precipitated calcium carbonate or otherminerals, are commonly compounded with plastics, such as polypropylene.Polymers compounded with fillers may require low moisture content,depending on the polymer/filler combination. For example, fine, brightcellulose particles generally need to be dry to be compatible withplastic. PVOH is less restrictive on moisture content than plastics.Fillers in water may be combined with PVOH and formed into fibers andfilms without drying beforehand. When PVOH is the polymer, finecellulose particles generally do not need to be pre-dried before mixingand forming fibers and films.

Based on the foregoing, there exists a need for cost-effective,water-based, filled PVOH fibers that can be incorporated into whitepaper products. Accordingly, it is to solving this and other needs thepresent invention is directed.

SUMMARY OF THE INVENTION

The present invention is directed to articles of manufacture. In oneaspect, the article is a fiber or a film. In another aspect, the articleincludes a PVOH and an inorganic filler comprising particles having anaverage diameter of less than about 20 micrometers. The PVOH has adegree of hydrolysis of greater than about 95% and is present in a rangebetween about 20 wt. % and about 99 wt. % based on the total articleweight.

Yet, in another aspect, the article includes a PVOH and an inorganicfiller comprising particles having an average diameter of less thanabout 20 micrometers. The PVOH has a degree of hydrolysis of greaterthan about 95%, is partially soluble in water at a temperature of lessthan about 95° C., and is present in a range between about 20 wt. % andabout 99 wt. % based on the total fiber weight.

Still yet, in another aspect, a method of making the article mixing aPVOH with a filler comprising particles having an average diameter ofless than about 20 micrometers and preparing an extrudable spin mass.The PVOH has a degree of hydrolysis of greater than about 95% and ispresent in a range between about 20 wt. % and about 99 wt. % based onthe total fiber weight.

It is to be understood that the phraseology and terminology employedherein are for the purpose of description and should not be regarded aslimiting. As such, those skilled in the art will appreciate that theconception, upon which this disclosure is based, may readily be utilizedas a basis for the designing of other structures, methods, and systemsfor carrying out the present invention. It is important, therefore, thatthe claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of the presentinvention.

Other advantages and capabilities of the invention will become apparentfrom the following description taken in conjunction with the examplesshowing aspects of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and the above object as well asobjects other than those set forth above will become apparent whenconsideration is given to the following detailed description thereof.Such description makes reference to the annexed drawings wherein:

The sole FIGURE is a photomicrograph of a polyvinyl alcohol film made inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

For a fuller understanding of the nature and desired objects of thisinvention, reference should be made to the above and following detaileddescription taken in connection with the accompanying FIGURE.

Terminology used herein is given its ordinary meaning consistent withthe exemplary definitions set forth immediately below; mg refers tomilligrams and m² refers to square meters, and so forth. Unlessotherwise specified, % means weight percent.

The terms “article of manufacture” or “article” as used herein meansfibers, films, and other shaped objects. The articles of manufactureinclude a binder and a filler. The binder is a polyvinyl alcohol (PVOH),cellulose nanofibrils, or a combination of the PVOH and cellulosenanofibrils. The filler is any combination of high brightness mineralfillers and cellulose fines.

The term “fiber” as used herein means an article in which the length todiameter ratio is greater than about 10. Alternatively, a fiber can havean average diameter in a range between about 10 and about 300micrometers.

The term “film” as used herein means an article which is a thin,flexible strip. A film can have an average thicknesses in a rangebetween about 10 and about 200 micrometers.

The term “inorganic filler” and “filler” as used herein means anyparticles, salts, or minerals having an average diameter of less thanabout 20 micrometers.

The term “degree of polymerization” (DP) as used herein means the numberof monomeric units in a polymer. For a homopolymer, such as PVOH, thereis only one type of monomeric unit; thus, the number-average DP is givenby M_(n)/M₀. M_(n) is the average molecular weight of the polymer, andM₀ is the molecular weight of the monomer unit.

The term “degree of hydrolysis” as used herein means the proportion ofacetate groups in polyvinyl acetate that have been converted to alcoholgroups to form the polyvinyl alcohol. The PVOH used in the presentinvention has a degree of hydrolysis of at least about 95%, which is theminimum threshold required to maintain water-solubility.

The term “substantially soluble in water” as used herein meanssubstantially dissolving in water at the provided temperature.Initially, the PVOH used is substantially soluble. The term “partiallysoluble in water” as used herein means partially dissolving in water atthe provided temperature. During processing and in the final article ofmanufacture, the PVOH is partially soluble in water.

The terms “wood pulp” and “pulp” as used herein refer to a cellulosicmaterial obtained from wood produced according to a chemical pulpingprocess including, but not limited to, sulfite pulping, kraft pulping,polysulfide pulping, and soda pulping processes. Non-limiting examplesof wood pulps include hardwood kraft pulp, softwood kraft pulp, hardwoodsulfite pulp, softwood sulfite pulp, or any combination thereof. Thecellulose fibers of the present invention can be derived from any typeof wood pulp. The pulp can be bleached by chemical means, for example bychlorine dioxide, oxygen, alkaline peroxide and so forth.

The term “papermaking fibers” as used herein includes virgin pulpderived fibers, recycled (secondary) cellulosic fibers, and fiber mixescomprising cellulosic fibers. Suitable papermaking fibers include, butare not limited to: nonwood fibers, such as cotton fibers or cottonderivative fibers, abaca fibers, kenaf fibers, sabai grass fibers,bamboo, flax fibers, esparto grass fibers, straw fibers, jute hempfibers, bagasse fibers, milkweed floss fibers, and pineapple leaffibers; and wood fibers, such as those obtained from deciduous andconiferous trees, including softwood fibers, such as northern andsouthern softwood Kraft fibers; hardwood fibers, such as eucalyptusfibers, maple fibers, birch fibers, aspen fibers, and the like.

Kraft softwood fiber is low yield fiber made by the Kraft (sulfate)pulping process from coniferous material and includes northern andsouthern softwood Kraft fiber, Douglas fir Kraft fiber and so forth.Kraft hardwood fiber is made by the Kraft process from hardwood sources,e.g., eucalyptus. Naturally occurring pulp-derived fibers are referredto herein simply as “pulp-derived” papermaking fibers. The fibers,films, papers, and products of the present invention can include blendsof conventional fibers (derived from virgin pulp or recycled sources).

The term “tissue furnish” as used herein refer to aqueous compositionscomprising fibers of this invention, cellulose fibers, papermakingfibers, or any combination thereof. Optionally, tissue furnishes includewet strength resins, debonders, other additives, and the like for makingpaper products. The term “tissue furnish” is used interchangeably with“fiber slurry.”

The term “waste paper” as used herein refers to paper or cardboardwhich, after use, is recovered in the form of recycled fiber and thenre-used to produce paper, cardboard, or paper products for some otherindustrial purpose. “Recycled” fiber thus refers to fiber material thathas previously been used in a paper or cardboard product.

The term “cellulose particle” as used herein means cellulose nanofibrilsor cellulose fines. Cellulose fines are small cellulose particlescommonly found in wood pulp. Cellulose fines can have dimensions in arange between about 1 and about 200 micrometers.

The term “cellulose nanofibrils” as used herein means “nanofibrillatedcellulose” (NFC), “microfibrillated cellulose” (MFC), cellulose fibrids,fibrillated lyocell, or any combination thereof. As used herein, theterms NFC and MFC are used interchangeably. Cellulose nanofibrils arederived from plant cell walls, which comprise microfibrils ornanofibrils composed of small bundles of cellulose chains. Themicrofibrils or nanofibrils can be isolated, which is described below,as collections or bundles of individual, isolated cellulose microfibrilsor nanofibrils. Cellulose nanofibrils can comprise hardwood kraft pulp,softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp, orany combination thereof. MFC and NFC can have average lengths in a rangebetween about 300 nanometers (nm) to about 4,500 nm. In addition, MFCand NFC can have average diameters in a range between about 3 nm toabout 100 nm. The aspect ratio is about 100 to about 150. An importantproperty of NFC, enabling it to function as a binder, is its ability tobond to tightly to itself upon drying that it does not re-disperse intoindividual nanofibrils upon rewetting.

The term “cellulose fibrid” as used herein means fine cellulose fibersproduced by regenerating cellulose (described in detail below).Cellulose fibrids can have average lengths in a range between about 300nm to about 4,500 nm. In addition, cellulose fibrids can have averagediameters in a range between about 3 nm to about 100 nm. The aspectratio is about 100 to 150.

The term “fibrillated lyocell” as used herein means a cellulose fiberobtained first by an organic solvent spinning process followedmechanical treatment that results in cellulose nanofibrils. The organicsolvent comprises a mixture of organic chemicals and water, and thesolvent spinning process involves dissolving cellulose in the organicsolvent to form a solution which is pumped through spinnerets to producefibers without formation of a derivative of the cellulose.

The terms “extrudable dope” and “extrudable spin mass” as used hereinare used interchangeably and means a composition including a binder, afiller, and optionally, a processing aid, that can be extruded throughan orifice, such as a spinneret to form shaped articles of manufacture,for example fibers and films. The binder is a polyvinyl alcohol (PVOH),cellulose nanofibrils, or a combination of the PVOH and cellulosenanofibrils, and the filler is any combination of high brightnessmineral and cellulose fines.

In the context of producing a cost-effective fiber or tissue product,the use of synthetic fibers or materials, such as PVOH, is a viableoption. PVOH is useful in papermaking applications because it can besubstantially soluble in water (before forming an article ofmanufacture), provides a substantial bonding effect, improves paperstrength, and is resistant to alkaline conditions. The solubility andbonding of the article may be changed during or after forming thearticle through various techniques if desired.

The present invention combines a PVOH with an inorganic filler to formarticles of manufacture and other shaped objects, for example fibers andfilms. In another aspect, inorganic filler can be incorporated into aPVOH, formed into a dried film, and ground to a particle size that canbe retained in a paper web. Paper webs and paper products include, butare not limited to, tissues, bath tissue, napkins, paper towels, facialtissues, filter paper, handsheets, and the like.

The PVOH and inorganic filler combination described herein provides forarticles of manufacture with optional levels of solubility, includingfibers and films. Thus, these articles can be incorporated into avariety of flushable and disposable products. Furthermore, the use ofvirgin inorganic fillers, as described herein, provides brightened andwhiter fibers and films.

Yet in another aspect of the present invention, a fiber includes a PVOHand an inorganic filler comprising particles having an average diameterof less than about 20 micrometers. The PVOH has a degree of hydrolysisof greater than about 95% and is present in a range between about 20 wt.% and about 99 wt. % based on the total fiber weight. The PVOH can beimpregnated with the filler, or the PVOH can encapsulate the filler.

The average diameter of the fibers of the present invention can be anydiameter, depending on the application. In one aspect, the fibers havean average diameter of less than about 300 micrometers. In anotheraspect, the fibers have an average diameter in a range between about 100micrometers and about 250 micrometers. Yet, in another, aspect, thefibers have an average diameter in a range between about 50 micrometersand about 100 micrometers. Yet, in another, aspect, the fibers have anaverage diameter in a range between about 10 micrometers and about 50micrometers. Still, in another aspect, the fibers have an averagediameter about or in the range between about 10, 20, 30, 40, 50, 60, 70,80, 90, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220,230, 240, 250, 260, 270, 280, 290, and 300 micrometers.

PVOH

PVOH such as MOWIOL® 10/98, which is commercially available from KurarayAmerica Inc., Houston, Tex., is one example of a suitable inputmaterial. In one aspect, the PVOH used in the present invention issubstantially soluble in water at a temperature of less than about 100°C. In another aspect, the PVOH is substantially soluble in water at atemperature of less than about 98° C. or about 95° C. Yet, in anotheraspect, the PVOH is substantially soluble in water at a temperature in arange between about 75° C. and about 95° C. Still yet, in anotheraspect, the PVOH is substantially soluble in water at a temperature ofless than about 85° C. In one aspect, the PVOH is substantially solublein water at a temperature about or in any range between about 50° C.,52° C., 55° C., 57° C., 60° C., 62° C., 65° C., 67° C., 70° C., 72° C.,75° C., 77° C., 80° C., 82° C., 85° C., 87° C., 90° C., 92° C., 95° C.,97° C., and 99° C.

However, although the PVOH is initially substantially soluble in waterat the provided temperature, the PVOH becomes either partially solublein water or substantially insoluble in water during processing andformation of the final article of manufacture. Thus, in the article ofmanufacture, the PVOH is partially soluble in water at a temperature ofless than about 98° C. or about 95° C. Yet, in another aspect, the PVOHis partially soluble in water at a temperature in a range between about75° C. and about 95° C. Still yet, in another aspect, the PVOH ispartially soluble in water at a temperature of less than about 85° C. Inone aspect, the PVOH is partially soluble in water at a temperatureabout or in any range between about 50° C., 52° C., 55° C., 57° C., 60°C., 62° C., 65° C., 67° C., 70° C., 72° C., 75° C., 77° C., 80° C., 82°C., 85° C., 87° C., 90° C., 92° C., 95° C., 97° C., and 99° C.

The PVOH can have an average degree of polymerization in a range betweenabout 500 and about 3,000. In one aspect, the PVOH has an average degreeof polymerization in a range between about 1,000 and about 1,600. Yet,in another aspect, the PVOH has an average degree of polymerization ofabout 1,400. Still, in another aspect, the PVOH has an average degree ofpolymerization about or in a range between about 500, 750, 1000, 1250,1350, 1400, 1500, 1600, 1700, 2000, 2500, and 3000.

The degree of hydrolysis of the PVOH is important for water solubilityand for mixing with fillers in water. The PVOH can have an averagedegree of hydrolysis of greater than about 95%. In another aspect, PVOHhas an average degree of hydrolysis of greater than about 98%. Yet, inanother aspect, the PVOH has an average degree of hydrolysis in a rangebetween about 95% to about 99%. Still, in another aspect, the PVOH hasan average degree of hydrolysis about or in a range between about 95%,96%, 97%, 98%, 99%, or 100%.

The PVOH can be present in the article in a range between about 20 wt. %and about 80 wt. % based on the total weight of the article, which canbe a fiber or a film. In one aspect, the PVOH is present in a rangebetween about 20 wt. % and about 99 wt. %. Yet, in another aspect, thePVOH is present in a range between about 40 wt. % and about 60 wt. %.Still yet, in another aspect, the PVOH is present in a range betweenabout 20 wt. % and about 99 wt. %. In another aspect, the PVOH ispresent in an amount about or in any range between about 20, 25, 30, 35,40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, and 99 wt. %.

In one aspect, the PVOH and inorganic filler is combined to form fibers.In another aspect, the PVOH and inorganic filler is combined to formfibrids. PVOH fibrids can be produced by mixing PVOH with the inorganicfiller to form a spin mass and then treating the spin mass with a shearfield in a coagulation bath, such as saturated sodium sulfate solution,to form the PVOH fibrids. For example, the method disclosed in CanadianPatent No. CA 2,313,213 for cellulose fibrids can be used to producefilled PVOH fibrids. Filled PVOH fibrids can have an average length ofabout 200 to about 2500 microns. In another aspect, filled PVOH fibridscan have an average length of about 600 to about 2000 microns. In yetanother aspect, filled PVOH fibrids can have an average length of about800 to about 1500 microns.

Optionally, the sodium sulfate coagulation bath can be acidified withsulfuric (or any other) acid. Acidification induces the calciumcarbonate inside the nascent fibrids to react with the acid and togenerate CO₂ and expand the fibrids. The result provides for bulkierpaper webs. Optional acids include hydrochloric acid, nitric acid,phosphoric acid, or any combination thereof. Optionally, sodiumbicarbonate can be added to generate more CO₂ and further increase fiberbulk.

Filler

The inorganic filler used in the present invention can be any inorganicparticle, material, mineral, or combination thereof, having an averagediameter of less than about 20 micrometers. In one aspect, the inorganicfiller comprises particles having an average diameter of about 1micrometer to about 18 micrometers. In another aspect, the inorganicfiller comprises particles having an average diameter of about 5micrometers to about 10 micrometers. Yet, in another aspect, theinorganic filler comprises particles having an average diameter of about2.5 micrometers to about 8 micrometers. Still yet, in another aspect,the inorganic filler comprises particles having an average diameter ofabout or in any range between about 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5,5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5,13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5,and 20 micrometers.

Non-limiting examples of suitable inorganic fillers include, but are notlimited to, precipitated calcium carbonate, ground calcium carbonate,gypsum, titanium dioxide, clay, silica, magnesium aluminum silicate,hydrated aluminum silicate, barium silicate, calcium silicate, magnesiumsilicate, strontium silicate, talc, mica, kaolin clay, sericite,muscovite, lepidolite, biotite, vermiculite, zeolite, barium sulfate,calcined calcium sulfate, hydroxyapatite, ceramic powder, colloidalsilicone dioxide, boron nitride, or any combination thereof.

The inorganic filler can be present in the article in a range betweenabout 1 wt. % and about 80 wt. % based on the total weight of thearticle. In one aspect, the article is a fiber or a film. In anotheraspect, the inorganic filler is present in a range between about 5 wt. %and about 50 wt. % based on the total weight of the article. Yet, inanother aspect, the inorganic filler is present in a range between about20 wt. % and about 60 wt. % based on the total weight of the article.Still yet, in another aspect, the inorganic filler is present in a rangebetween about 30 wt. % and about 50 wt. % based on the total weight ofthe article. Still, in another aspect, the inorganic filler is presentin an amount about or in a range between about 1, 2.5, 5, 7.5, 10, 12.5,15, 17.5, 20, 25, 30, 35, 40, 42.4, 45, 47.5, and 50 wt. % based on thetotal weight of the article.

Cellulose fines can be incorporated into the articles of the presentinvention. In one aspect, the cellulose fines can have an averagediameter in a range between about 1 micrometer and about 40 micrometers.Yet, in another aspect, the cellulose fines have an average dimensionsabout or in a range between about 1, 10, 20, 30, 40, 50, 60, 70, 80, 90,100, 110, 120, 130, 140, 150, 160, 170, 180, 190, and 200 micrometers.

The physical properties of the PVOH of the present invention enableformation of a solid article of manufacture, including a fiber and afilm, with limited solubility upon drying and after treatment. Inaddition, these PVOH in combination with the inorganic filler can dryinto fibers, films, or other shaped objects. Further, the PVOH can trap,encapsulate, and bind small particles in the inorganic filler as thespin mass is extruded to form the objects. The fibers and films remainsubstantially in their shaped state when immersed in water or an aqueousenvironment. The objects can then be readily formed, retained, andbonded into a paper web.

As indicated above, a film of the present invention includes a PVOH andinorganic filler. The sole FIGURE illustrates a photomicrograph of aPVOH film. The PVOH film includes 55% PVOH, 33% PCC, and 11% cellulosefibers obtained from hardwood kraft pulp.

When used to produce a film, the PVOH can be impregnated with theinorganic filler, or the PVOH can encapsulate the inorganic filler. Thefilms can have any average thickness, which depends on the application.In one aspect, the films have an average thickness in a range betweenabout 10 micrometers to about 200 micrometers. In another aspect, thefilms have an average thickness in a range between about 50 micrometersto about 150 micrometers. Yet in another aspect, the films have anaverage thickness in a range between about 40 micrometers to about 100micrometers.

In addition to fibers and films, papers can include PVOH and inorganicfillers. In another aspect of the present invention, a paper comprises acellulosic substrate having a surface and a mixture being substantiallydisposed onto the surface or impregnating the cellulosic substrate. Themixture comprises a PVOH and an inorganic filler. The PVOH fibers formedcan be incorporated into any paper or paper product.

Cellulose

In one aspect, the articles described herein can further include anypulp, cellulose particles, cellulose fibers, papermaking fibers, or anycombination thereof. The cellulose particles can be cellulosenanofibrils or cellulose fines. Cellulose particles include, but are notlimited to, hardwood kraft pulp particles, softwood kraft pulpparticles, hardwood sulfite pulp particles, softwood sulfite pulpparticles, grass pulp particles, or any combination thereof.

Cellulose nanofibrils, including NFC, can be combined or mixed with theinorganic filler and any suitable additives or processing aids to form aspin mass. NFC can be isolated by mechanical disintegration of the plantcell wall in wood pulp. In addition to mechanical force, variouschemical pre-treatments, such as strong hydrolysis, can be used.Mechanical disintegration of NFC from cellulose raw material, cellulosepulp, wood pulp, or refined pulp is carried out with any suitableequipment, such as a refiner, a grinder, a homogenizer, a colloider, afriction grinder, an ultrasound sonicator, a fluidizer, such as a microfluidizer, a macro fluidizer or a fluidizer-type homogenizer. U.S.Patent Pub. No. 2012/0214979 A1 to Heiskanen et al. (now U.S. Pat. No.7,747,612), which is incorporated herein in its entirety by reference,discloses an exemplary method for isolating NFC.

NFC also can be chemically or physically modified to form a derivativeof cellulose or microfibril bundles. The chemical modification can bebased, for example, on carboxymethylation, oxidation, esterification, oretherification reactions of cellulose molecules. Modification also isaccomplished by physical adsorption of anionic, cationic, non-ionicsubstances, or any combination of thereof, onto the cellulose surface.The described modifications can be carried out before, after, or duringthe production of NFC.

Any of the above described methods for producing cellulose nanofibrilscan be used in the present invention. In addition, any other suitablemethod known in the art can be used to produce the cellulosenanofibrils.

Cellulose fibrids can be produced by regenerating cellulose, forexample, by initially dissolving cellulose or a cellulose derivative ina solvent to produce a cellulose spin mass. Following dissolution in asuitable solvent, mixing in a high-shear mixer can produce finelydispersed cellulose fibrids. These fibrids, like NFC, are fine enoughthat they form films, and other structures, that do not re-disperse uponwetting in water. Cellulose fibrids can be combined and mixed withinorganic fillers and any suitable additives or processing aids to forma spin mass. Subsequently, the spin mass can be extruded throughspinnerets to form the fibers and films.

Exemplary methods of forming cellulose fibrids are disclosed in U.S.Pat. Nos. 2,999,788 to Morgan and 6,451,884 to Cowen et al., both ofwhich are incorporated herein in their entirety by reference. Asdisclosed in U.S. Pat. No. 2,999,788, cellulosic fibrids can be made bymixing a spinning solution of cellulose and coagulating liquor togetherunder turbulent conditions. One example of such a spinning solution isviscose, which contains sodium cellulose xanthate. Examples ofcoagulating liquors for viscose include, but are not limited to, aqueoussalt solutions and aqueous acid solutions.

Canadian Patent No. CA 2,313,213, which is incorporated herein in itsentirety by reference, describes an exemplary method of fibridproduction using shear coagulation of a cellulose spin mass made withN-methylmorpholine N-oxide (NMMO or NMMNO). Briefly, a method ofproducing reactive fiber-like cellulose coagulates comprises steps ofproviding a solution of cellulose in a mixture containing water andNMMO, and then treating the solution in a precipitation bath containingwater and NMMO with a shear field. The method has the advantage that nostretching or drawing in air in another non-precipitating medium isrequired for orienting the cellulose molecules along the fiber axis.Instead, the coagulates can directly be obtained in a precipitation pathusing a shear field generator. The shear field can be produced bysurfaces that are closely arranged side by side and are movable relativeto one another.

A method for dissolving cellulose to produce a cellulose spin mass isdisclosed in U.S. Pat. No. 4,246,221 to McCorsley, which is incorporatedherein in its entirety by reference. In addition, cellulose can bedissolved in a solution of a tertiary amine N-oxide to produce a spinmass. One process for dissolving cellulose in a tertiary amine N-oxideis disclosed, for example, U.S. Pat. No. 2,179,181 to Graenacher et al.,which is incorporated herein in its entirety by reference. In accordancewith the disclosure, oxides of trimethylamine, triethylamine,tripropylamine, monomethyldiethylamine, dimethylmonoethylamine,monomethyldipropylamine, N-dimethyl-, N-diethyl- orN-dipropylcyclohexylamine, N-dimethylmethylcyclohexylamine and pyridinecan be used. U.S. Pat. No. 3,447,939 to Johnson, which is incorporatedherein in its entirety by reference, discloses a process for dissolvingcellulose in an anhydrous tertiary amine N-oxide, which is incorporatedherein in its entirety by reference. A cyclic mono(N-methylamine-N-oxide) compound, such as NMMO is used as the solvent.

Any of the above described methods for producing cellulose fibrids canbe used in the present invention. In addition, any other suitable methodknown in the art can be used to produce the cellulose fibrids.

Any of the above mentioned cellulose nanofibrils of the presentinvention can have an average length of less than about 800 micrometers.In another aspect, the cellulose nanofibrils have an average length in arange between about 300 micrometers to about 700 micrometers. Yet, inanother aspect, the cellulose nanofibrils have an average length in arange between about 100 micrometers to about 500 micrometers. Still yet,in another aspect, the cellulose nanofibrils have an average length ofless than about 200 micrometers. In one aspect, the cellulosenanofibrils have an average length about or in any range between about100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750,and 800 micrometers.

Any of the cellulose nanofibrils can be present in the fibers or filmsin a range between about 1 wt. % to about 80 wt. % based on the totalweight of the fiber or film. In another aspect, the cellulosenanofibrils can be present in the fibers or films in a range betweenabout 5 wt. % to about 70 wt. % based on the total weight of the fiberor film. Yet, in another aspect, the cellulose nanofibrils can bepresent in a range between about 20 wt. % to about 50 wt. % based on thetotal weight of the fiber or film. Still, in another aspect, thecellulose nanofibrils can be present in an amount about or in a rangebetween about 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70,75, and 80 wt. % based on the total weight of the fiber or film.

Additives

The articles described herein, which can be fibers or films can includeany suitable processing aids or additives, which can aid in forming aspinnable or extrudable spin mass. The processing aid can be present ina range between about 0.5 wt. % to about 10 wt. %. In another aspect,the processing aid can be present in the spin mass in a range betweenabout 0.3 wt. % to about 5 wt. %. In yet another aspect, the processingaid can be present in the cellulose spin mass in a range between about0.5 wt. % to about 2 wt. %. Still, in another aspect, the processingaids are present in an amount about or in any range between about 0.1,0.2, 0.5, 0.7, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, and 5.0 wt. %.Non-limiting examples of suitable processing aids includecarboxymethylcellulose, starch, glyoxal, glutaraldehyde, boric acidcarbonate, zirconium ammonium carbonate, glyoxalated polyacrylamide,polyamide-epichlorohydrin, polyamine-epichlorohydrin, urea-formaldehyde,melamine-formaldehyde, polyethyleneimine, propylene glycol, diethyleneglycol, triethylene glycol, dipropylene glycol, glycerol, triacetin(glycerol triacetate), diethylene glycol diacetate, triethylene glycoldiacetate, tripropionin, acetyl triethyl citrate, triethyl citrate, orany combination thereof.

Optionally, an acid can be added to the PVOH and organic fillercombination to generate CO₂, which results in expanded fibers and canlead to bulkier paper webs. Alternatively, sodium bicarbonate can beadded to generate even more CO₂. Optional acids include sulfuric acid,hydrochloric acid, nitric acid, phosphoric acid, or any combinationthereof.

Method of Making

In accordance with the present invention, a method of making thearticles described herein, which can be fibers or films, includes mixinga PVOH with an inorganic filler with particles having an averagediameter of less than about 20 micrometers and preparing an extrudablespin mass. In one aspect, the PVOH has a degree of hydrolysis of greaterthan about 95% and is present in a range between about 20 wt. % andabout 99 wt. % based on the total fiber weight.

Initially, the PVOH is mixed with inorganic filler, and optionally,processing aids and cellulose particles, to form an extrudable spinmass. When cellulose nanofibrils, cellulose nanocrystals, or cellulosefibrids are included, additives such as carboxymethyl cellulose can beadded to increase the extensibility of the spin mass. The properties ofthe PVOH are chosen to obtain the desired rheology.

The fibers can be formed from the spin mass using various methods,including, for example, wet spinning, dry spinning, shear spinning, orslit extruding. Films also can be formed by an extrusion process. In asolution spinning process, the extrudable spin mass is delivered toorifices of a spinneret. As one of ordinary skill in the art willunderstand, a spinneret refers to a portion of a fiber forming apparatusthat delivers molten, liquid, or dissolved materials through orificesfor extrusion into an outside environment. A spinneret includes fromabout 1 to about 500,000 orifices per meter of length of the spinneret.A spinneret can be implemented with holes drilled or etched through aplate, or with any other structure capable of issuing desired fibers.

Upon emerging from the spinneret, the PVOH and inorganic fillercombination solidifies to form the fibers or films. In a wet solutionspinning process, the spinneret can be submerged in a coagulation orspinning bath (e.g., a chemical bath), such that upon exiting thespinneret, one or more materials can precipitate and form solid fibers.The composition of the spinning bath can vary depending upon the desiredapplication of the resulting fibers. For example, the spinning bath canbe water, an acidic solution (e.g., a weak acid solution includingsulfuric acid), or a salt bath using sodium sulfate for example. In adry solution spinning process, one or more materials can emerge from thespinneret in warm air and solidify due to a solvent (e.g., acetone)evaporating in the warm air.

After emerging from the spinneret, fibers can be drawn or stretchedutilizing a godet or an aspirator. For example, fibers emerging from thespinneret can form a vertically oriented curtain of downwardly movingfibers that are drawn between variable speed godet rolls before beingwound on a bobbin or cut into staple fiber. Fibers emerging from thespinneret can also form a horizontally oriented curtain within aspinning bath and can be drawn between variable speed godet rolls. Asanother example, fibers emerging from the spinneret can be at leastpartially quenched before entering a long, slot-shaped air aspiratorpositioned below the spinneret. The aspirator can introduce a rapid,downwardly moving air stream produced by compressed air from one or moreair aspirating jets. The air stream can create a drawing force on thefibers, causing them to be drawn between the spinneret and the air jetand attenuating the fibers. During this portion of fiber formation, oneor more polymer materials forming the fibers can be solidifying.

Following extrusion from the spinnerets, the shaped fibers or films canbe dried by any suitable method. For example, the fibers or films can beair-dried. Alternatively, the fibers or films can be dried in a hot airstream. These fibers can be incorporated into a paper web.

Fibers can be formed with or without additional fillers to produceunique cellulose shapes beneficial to paper properties. U.S.2006/0012072 to Hagewood et al. discloses methods for forming variousshaped fibers, which is incorporated herein in its entirety byreference.

In one aspect of the present invention, a method of making a papercomprises initially forming a mixture (or composite) of PVOH and aninorganic filler. Then, the method includes incorporating the mixtureinto a tissue furnish (or adding the composite to the tissue furnish),forming a nascent web, and then drying the nascent web to form thepaper, handsheet, or tissue. Alternatively, the method of making thepaper includes forming the nascent web, dewatering the nascent web,substantially disposing the mixture onto the surface of the nascent web,and then drying the nascent web to form the paper. The nascent web canbe dried by air-drying, through-air drying (TAD), drum drying (e.g.,drying on the surface of a Yankee dryer), or any combination thereof.

Optionally, the PVOH fibers are cut into short staple fibers prior tobeing added to the tissue furnish. One potential advantage of employingstaple fibers is that a more isotropic web can be formed, since thestaple fibers can be oriented in the web more randomly than longerfibers.

In another aspect, a tissue furnish of cellulose fibers can be depositedonto a forming surface to form a nascent web. Then, the mixture of PVOHand inorganic filler can be substantially disposed onto the surface ofthe nascent web by spraying or any suitable application method.Alternatively, the mixture can be substantially disposed onto thesurface of the paper after an initial drying process. For example, themixture can be substantially disposed, i.e., by spraying, onto thesurface of the paper after drying on a Yankee dryer, but prior to dryingby a second drying method.

In another aspect, an inorganic filler and PVOH are combined to form amixture, and then the mixture is dried and ground to an average particlesize in a range between about 1 micrometer to about 80 micrometers. Yet,another aspect, the mixture is dried and ground to an average particlesize in a range between about 5 micrometers to about 50 micrometers.Still yet, in another aspect, the mixture is dried and ground to anaverage particle size in a range between about 10 micrometers to about25 micrometers. In one aspect, the mixture is dried and ground to anaverage particle size in a range between about 1, 5, 10, 15, 20, 25, 30,35, 40, 45, 50, 55, 60, 65, 70, 75, and 80 micrometers. Then, themixture can be added to a tissue furnish. Retention aids can be added tothe tissue furnish if necessary. Alternatively, the mixture isspray-dried with a particle size that can be retained in a tissuefurnish. A method of spray-drying is described in U.S. Pat. No.8,372,320 to Gardner et al., which is incorporated herein in itsentirety by reference.

With respect to the above description, it is to be realized that theoptimum proportional relationships for the parts of the invention, toinclude variations in components, concentration, shape, form, function,and manner of manufacture, and use, are deemed readily apparent andobvious to one skilled in the art, and all equivalent relationships tothose illustrated in the specification are intended to be encompassed bythe present invention.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, various modifications may be made of theinvention without departing from the scope thereof, and it is desired,therefore, that only such limitations shall be placed thereon as areimposed by the prior art and which are set forth in the appended claims.

What is claimed is:
 1. An article of manufacture comprising: a polyvinylalcohol (PVOH) and an inorganic filler comprising particles having anaverage diameter of less than about 20 micrometers, the PVOH having adegree of hydrolysis of greater than about 95% and being present in arange between about 20 wt. % and about 99 wt. % based on the totalarticle weight.
 2. The article of claim 1, wherein the article is afiber or a film.
 3. The article of claim 2, wherein the inorganic fillerparticles have an average diameter of less than about 3 micrometers. 4.The article of claim 2, wherein the inorganic filler is present in arange between about 1 wt. % and about 50 wt. % based on the total fiberweight.
 5. The article of claim 2, wherein the inorganic filler isprecipitated calcium carbonate, ground calcium carbonate, gypsum,titanium dioxide, clay, silica, or any combination thereof.
 6. Thearticle of claim 2, wherein the PVOH is present in a range between about40 wt. % and about 60 wt. % based on the total weight of the fiber orthe film.
 7. The article of claim 2, wherein the PVOH has a degree ofpolymerization in a range between about 500 and about 3,000.
 8. Thearticle of claim 7, wherein the degree of polymerization is in a rangebetween about 1,000 and about 1,600.
 9. The article of claim 2, whereinthe degree of hydrolysis is greater than about 98%.
 10. The article ofclaim 2, further comprising cellulose particles in a range between about1 wt. % and about 50 wt. % based on the total weight of the fiber or thefilm.
 11. The article of claim 10, wherein the cellulose particles arecellulose nanofibrils or cellulose fines.
 12. The article of claim 11,wherein the cellulose particles are hardwood kraft pulp particles,softwood kraft pulp particles, hardwood sulfite pulp particles, softwoodsulfite pulp particles, grass pulp particles, or any combinationthereof.
 13. The article of claim 1, further comprising a processingaid.
 14. The article of claim 13, wherein the processing aid is presentin a range between about 0.5 wt. % and about 10 wt. % based on the totalfiber weight.
 15. The article of claim 13, wherein the processing aid iscarboxymethylcellulose, starch, glyoxal, glutaraldehyde, dialdehydesboric acid carbonate, zirconium ammonium carbonate, glyoxalatedpolyacrylamide, polyamide-epichlorohydrin, polyamine-epichlorohydrin,urea-formaldehyde, melamine-formaldehyde, polyethyleneimine, propyleneglycol, diethylene glycol, triethylene glycol, dipropylene glycol,glycerol, or any combination thereof.
 16. The article of claim 1,wherein the PVOH is partially soluble in water at a temperature of lessthan about 98° C.
 17. The article of claim 16, wherein the PVOH ispartially soluble in water at a temperature in a range between about 75°C. and about 95° C.
 18. The article of claim 1, further comprising aCO₂-generating acid.
 19. The article of claim 1, further comprisingCO₂-generating sodium bicarbonate.
 20. An article of manufacturecomprising: a PVOH and an inorganic filler comprising particles havingan average diameter of less than about 20 micrometers, the PVOH having adegree of hydrolysis of greater than about 95%, being partially solublein water at a temperature of less than about 95° C., and being presentin a range between about 20 wt. % and about 99 wt. % based on the totalfiber weight.
 21. The article of claim 20, wherein article is a fiber ora film.
 22. The article of claim 21, wherein the inorganic fillerparticles have an average diameter of less than about 3 micrometers. 23.The article of claim 21, wherein the inorganic filler is present in arange between about 1 wt. % and about 50 wt. % based on the total fiberweight.
 24. The article of claim 21, wherein the filler is precipitatedcalcium carbonate, ground calcium carbonate, gypsum, titanium dioxide,clay, silica, or any combination thereof.
 25. The article of claim 21,wherein the PVOH is present in a range between about 40 wt. % and about60 wt. % based on the total weight of the fiber.
 26. The article ofclaim 21, wherein the PVOH has a degree of polymerization in a rangebetween about 500 and about 3,000.
 27. The article of claim 26, whereinthe degree of polymerization is in a range between about 1,000 and about1,600.
 28. The article of claim 21, wherein the degree of hydrolysis isgreater than about 98%.
 29. The article of claim 21, further comprisingcellulose particles in a range between about 1 wt. % and about 50 wt. %based on the total weight of the fiber.
 30. The article of claim 29,wherein the cellulose particles are cellulose nanofibrils or cellulosefines.
 31. The article of claim 29, wherein the cellulose particles arehardwood kraft pulp particles, softwood kraft pulp particles, hardwoodsulfite pulp particles, softwood sulfite pulp particles, grass pulpparticles, or any combination thereof.
 32. The article of claim 21,further comprising a processing aid.
 33. The article of claim 32,wherein the processing aid is present in a range between about 0.5 wt. %and about 10 wt. % based on the total fiber weight.
 34. The article ofclaim 32, wherein the processing aid is carboxymethylcellulose, starch,glyoxal, glutaraldehyde, dialdehydes boric acid carbonate, zirconiumammonium carbonate, glyoxalated polyacrylamide,polyamide-epichlorohydrin, polyamine-epichlorohydrin, urea-formaldehyde,melamine-formaldehyde, polyethyleneimine, propylene glycol, diethyleneglycol, triethylene glycol, dipropylene glycol, glycerol, or anycombination thereof.
 35. The article of claim 21, wherein the PVOH ispartially soluble in water at a temperature in a range between about 75°C. and about 95° C.
 36. The article of claim 21, further comprising aCO₂-generating acid.
 37. The article of claim 21, further comprisingCO₂-generating sodium bicarbonate.
 38. A method of making an article ofmanufacture, the method comprising: mixing a PVOH with an inorganicfiller comprising particles having an average diameter of less thanabout 20 micrometers, the PVOH having a degree of hydrolysis of greaterthan about 95% and being present in a range between about 20 wt. % andabout 99 wt. % based on the total fiber weight; and preparing anextrudable spin mass.
 39. The method of claim 38, wherein the article isa fiber or a film.
 40. The method of claim 39, further comprising wetspinning, dry spinning, shear spinning, or slit extruding the extrudablespin mass to form the fiber or the film.
 41. The method of claim 39,further comprising mixing the PVOH, the filler, or both with celluloseparticles.
 42. The method of claim 41, wherein the cellulose particlesare cellulose nanofibrils or cellulose fines.
 43. The method of claim42, wherein the cellulose particles are derived from hardwood kraftpulp, softwood kraft pulp, hardwood sulfite pulp, softwood sulfite pulp,grass pulp, or any combination thereof.
 44. The method of claim 41,further comprising extracting the cellulose particles from waste paper,seed pods, algae, bacteria, tunicates, or any combination thereof. 45.The method of claim 41, wherein the PVOH has a degree of polymerizationin a range between about 500 and about 3,000.
 46. The method of claim45, wherein the degree of polymerization is in a range between about1,000 and about 1,600.
 47. The method of claim 39, wherein the degree ofhydrolysis is greater than about 98%.
 48. The method of claim 39,wherein the PVOH is substantially soluble in water at a temperature ofless than about 98° C.
 49. The method of claim 39, wherein the PVOH issubstantially soluble in water at a temperature in a range between about75° C. and about 95° C.
 50. The method of claim 39, further comprisingmixing the PVOH and the inorganic filler with sodium bicarbonate togenerate CO₂ and increase bulk.